Early intervention with Si Ni Decoction enhances growth performance and immune status in broilers via modulation of gut microbiota and barrier function

This study aims to investigate the effects of early intervention with Si Ni Decoction (SND) on the growth performance, intestinal morphology, and microbiota of broiler chickens. A total of 288 one-day-old AA broilers were randomly assigned to four groups: control group (CON), low-dose SND group (LSND), medium-dose SND group (MSND), and high-dose SND group (HSND). During the first five days of the experiment, different doses of SND (0, 1.25, 2.5, and 5.0 mL/L) were added to the drinking water of each group, with the experiment lasting for a total of 42 days. The results indicated that SND significantly increased final weight of chickens at 6, 21, and 42 days of age, as well as ADG from 1 to 6 days and from 1 to 21 days, and reduced FCR from 1 to 42 days. SND enhanced the immune organ indices, antibody titers for AI and ND, and serum levels of IgA, IgG, and IgM, and decreased levels of IL-1β, IL-6, and TNF-α. Additionally, SND upregulated the mRNA expression levels and protein abundance of ZO-1, Claudin-1, and Occludin, increased the height of jejunal villi, and promoted intestinal barrier development. Furthermore, SND improved both alpha and beta diversity of cecal microbiota at 6 days of age and increased the abundance of beneficial bacteria such as Bacteroidetes, Lactobacillus, and Ruminococcus_torques_group and reduced the abundance of Proteobacteria and Escherichia_Shigella. In conclusion, this study demonstrates that addition of SND to the drinking water of chicks from 1 to 5 days of age can modulate immune status, promote intestinal development, and regulate gut microbiota composition, thereby enhancing their production performance.